1. Bones and Skeletal Tissues6

2. Skeletal Cartilage Avascular & without nerves
Vascularized perichondrium
Three types
Hyaline
Elastic
Fibrocartilage

3. 2 types of growth Calcification Growth of Cartilage
Appositional –perichondrium cells secrete matrix
Interstitial – chondrocytes within cartilage secrete matrix
Calcification
bone growth
geriatric

4. Classification of Bones by Skeletal Region
Axial skeleton
skull, vertebral column, ribs & sternum
Appendicular skeleton
limbs, pectoral girdle, & pelvic girdle

5. Classification of Bones: By Shape
Long bones
Figure 6.2a

6. Classification of Bones: By Shape
Long bones
Short bones
Cube-shaped carpals, tarsals, & patella
Figure 6.2b

7. Classification of Bones: By Shape
Long bones
Short bones
Flat bones
sternum, & most skull bones
Figure 6.2c

8. Classification of Bones: By Shape
Long bones
Short bones
Flat bones
Irregular bones
Vertebrae & pelvic bones
Figure 6.2d

9. Gross Anatomical Bone Features
Bulges, depressions, and holes that serve as:
Attachment sites for ligaments & tendons (muscles)
Joint surfaces
Conduits for blood vessels and nerves
Table 6.1
Know It

10. Gross Anatomy: Structure of Long Bone
Figure 6.3

11. Periosteum – Endosteum Bone Membranes
Outer – dense, regular connective tissue
Inner (osteogenic) - osteoblasts and osteoclasts
nerves, blood, & lymphatic vessels enter via nutrient foramina
Secured to underlying bone by Sharpey’s fibers
Endosteum
Thin membrane covering internal surfaces of bone
Endosteum

12. Structure of Short, Irregular, and Flat Bones
Periosteum-covered compact bone on the outside
Endosteum-covered spongy bone (diploë) on the inside
no diaphysis or epiphyses
Red marrow among trabeculae of diploë

13. Red Yellow Bone Marrow Hematopoietic stem cells childhood
medullary cavity & all areas of spongy bone
adults
diploë of flat bones, head of the femur & humerus
Yellow
Adipose-like tissue
Medullary cavity & epiphyseal spongy bone

14. Microscopic Structure of Bone: Compact Bone
Osteoid
Ossified minerals

15. Composition of Bone: Components
Osteocytes – mature bone cells
Osteoblasts – bone-forming cells
Osteoclasts – resorb or break down bone matrix
Osteoid – unmineralized ECM of proteoglycans & collagen
Hydroxyapatite
calcium phosphates
65% of bone by mass

16. Osteogenesis begins by 8th week of embryonic development
Bone Development
Chondrogenesis forms cartilaginous model of skeleton in embryos beginning in 6th week
Osteogenesis begins by 8th week of embryonic development
collagen matrix
Ossification
Intramembranous
develops within a fibrous membrane
Endochondral
replacement of hyaline cartilage model

17. Intramembranous Ossification
Formation of most of the flat bones of the skull and the clavicles
Fibrous connective tissue membranes are formed by mesenchymal cells

18. Stages of Intramembranous Ossification

19. Stages of Intramembranous Ossification

20. Endochondral Ossification
Formation of the long bones and many irregular bones (vertebrae)
Chondrocytes 1st form cartilaginous model of the bone that is replaced by osteoblasts and then mineralized

21. Stages of Endochondral Ossification
Hyaline cartilage
Primary ossification center
Bone collar 1

22. Stages of Endochondral Ossification
Deteriorating cartilage matrix
Hyaline cartilage
Primary ossification center
Bone collar 1 2

23. Stages of Endochondral Ossification
Deteriorating cartilage matrix
Hyaline cartilage
Spongy bone formation
Primary ossification center
Bone collar
Blood vessel of periosteal bud 1 2 3

24. Stages of Endochondral Ossification
Secondary ossification center
Epiphyseal blood vessel
Deteriorating cartilage matrix
Hyaline cartilage
Spongy bone formation
Primary ossification center
Medullary cavity
Bone collar
Blood vessel of periosteal bud 1 2 3 4

25. Stages of Endochondral Ossification
Secondary ossification center
Articular cartilage
Epiphyseal blood vessel
Spongy bone
Deteriorating cartilage matrix
Hyaline cartilage
Epiphyseal plate cartilage
Spongy bone formation
Primary ossification center
Medullary cavity
Bone collar
Blood vessel of periosteal bud 1 2 3 4 5
Figure 6.8

26. Functional Zones in Long Bone Growth

27. Long Bone Growth and Remodeling
Figure 6.10

28. Appositional Growth of Bone
Central canal of osteon
Periosteal ridge
Periosteum
Penetrating canal
Artery 1
Osteoblasts beneath periosteum secrete bone matrix & form ridges following periosteal blood vessels 2
As the ridges meet, they form a tunnel containing the blood vessel 3
The periosteum lining the tunnel is transformed into an endosteum and the osteoblasts just deep to the tunnel endosteum secrete bone matrix, narrowing the canal. 4
As the osteoblasts beneath the endosteum form new lamellae, a new osteon is created. Meanwhile new circumferential lamellae are elaborated beneath the periosteum and the process is repeated, continuing to enlarge bone diameter.
Figure 6.11

29. Hormonal Regulation of Bone Growth
During infancy and childhood, epiphyseal plate activity is stimulated by growth hormone
During puberty, testosterone and estrogens:

30. Requires protein, vitamins C, D, A, Ca, P, Mg, & Mn Resorption
Bone Remodeling
Osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces
Requires protein, vitamins C, D, A, Ca, P, Mg, & Mn
Resorption
Osteoclasts in resorption bays secrete
enzymes that digest matrix
acids that dissolve Ca salts
Deposition
Osteoblasts
Lay down fresh osteoid matrix and induce mineralization

31. Mechanical and gravitational forces
Control of Remodeling
Hormonal control loops regulate bone remodeling & maintain Ca homeostasis in the blood
Mechanical and gravitational forces

32. Hormonal Mechanism
Figure 6.12

33. Importance of Ionic Calcium in the Body
Transmission of nerve impulses
Muscle contraction
Blood coagulation
Secretion by glands and nerve cells
Cell division

34. Response to Mechanical Stress
Wolff’s law –
A bone grows and/or remodels in response to mechanical stresses
Bones are thickest where the stresses are maximal
Long bones - midway along the shaft
Curved bones where the curvature is greatest
Trabeculae form along lines of stress
Large, bony projections occur where heavy, active muscles attach

35. Response to Mechanical Stress
Figure 6.13

36. Bone Fracture Classification
Position of the bone ends
nondisplaced v displaced
Completeness of the break
Orientation of the break to the long axis
linear v transverse
Whether or not the ends penetrate skin
compound v simple

37. Common Types of Fractures

38. Common Types of Fractures

39. Common Types of Fractures

40. Stages in the Healing of a Bone Fracture
Hematoma formation
Hematoma 1
Hematoma formation
Figure

41. Stages in the Healing of a Bone Fracture
Fibrocartilaginous callus formation (soft callus)
Granulation tissue (fibrocartilage) grows
Capillaries grow and phagocytic cells clear debris
External callus
New blood vessels
Internal callus (fibrous tissue and cartilage)
Spongy bone trabeculae 2
Fibrocartilaginous callus formation
Figure

42. Stages in the Healing of a Bone Fracture
Bony callus formation
fibrocartilage of fibrocartilaginous callus converts into spongy bone
Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later
Bony callus of spongy bone 3
Bony callus formation
Figure

43. Stages in the Healing of a Bone Fracture
Bone remodeling
Excess material on is removed
Compact bone is laid down to reconstruct shaft walls
Healing fracture 4
Bone remodeling
Figure

44. Homeostatic Imbalances
Ca deficiency conditions
Dietary or hormonal (vit D)
Inadequate mineralization causing softened, weakened bones
Osteomalacia
elderly
Rickets
children

45. Osteoporosis Pathology Preventive measures Treatments
Condition when bone reabsorption outpaces bone deposit
Spongy bone is most vulnerable (especially spine)
Bones become very fragile
Occurs most often in postmenopausal women
Preventive measures
Dietary Ca and vitamin D
Increased weight-bearing exercise
Treatments
Hormone replacement therapy (HRT) – estrogens
Statins

46. Excessive bone remodeling
Paget’s Disease
Excessive bone remodeling
Initially, an excess of spongy to compact bone forms
Later, osteoclast activity wanes, but osteoblast activity continues resulting in filling in spongy bone and loss of marrow
Usually localized in the spine, pelvis, femur, and skull

47. Developmental Aspects of Bones
Mesoderm gives rise to embryonic mesenchymal cells, which produce membranes and cartilages that form the embryonic skeleton
The embryonic skeleton ossifies in a predictable timetable that allows fetal age to be easily determined from sonograms
At birth, most long bones are well ossified (except for their epiphyses)
By age 25, nearly all bones are completely ossified
In old age, bone resorption predominates